By Kanishka SinghWASHINGTON, April 2 (Reuters) - Dozens of international law experts in the U.S. have signed an open letter saying that American strikes on Iran may amount to war crimes, after President Donald Trump reiterated his threats this week to strike Iran's power and desalination plants.Trump, who has previously offered shifting timelines and objectives for the war, said in a televised speech on Wednesday that the war could escalate if Iran did not give in to Washington's terms, with str...